Problem: Solve for $y$ : $-18 = y + 25$
Solution: Subtract $25$ from both sides: $ \begin{eqnarray} \\ \hphantom{-18 {- 25}} &\hphantom{=}& \hphantom{y} \\ -18 &=& y + 25 \\ \\ {-25} && {-25} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ -18 {- 25} &=& y \\ \end{eqnarray} $ Simplify. $ y = -43$